Process of electrolytically removing scale and producing iron sulfate.



i the iron article is made the lytic UNITED STATES PATEN T QFFTOE.

CHARLES J. REED, OF PHILADELPHIA, PENNSYLVANIA. PROCESS OF ELECTROLYTICALLY REMOVING SCALE AND PRODUCING IRON SULFATE.

.Specification of Letters Patent.

Patented June 4, 1907.

Application filed June 18,1906. Serial No. 322,270.

To all whom, it may concern:

Be it known that I, CHARLES J. REED, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Processes of Electrolytically Removing Scale and Producing Iron Sulfate, of which the following is a specification.

Various electrolytic methods have been proposed for removing the oxid scale from iron sheets, rods and wire. Insome of these anode in an electrolyte of acid or an acid salt. The scale is thus dissolved more rapidly than in the usual pickle bath but the action is apt to be irregular and solution of the iron invariably oc curs. Furthermore the gain in time is more than offset by the cost of the electric current. In other proposed methods the iron article is made the cathode in an electrolyte which is neutral, weakly acid or alkaline, for example, a dilute solution of an alkali-metal salt, an acid or an alkali. The removal of scale, however, is slow and irregular, spots of scale being frequently left at various points. Some of the scale is also loosened by the electrohydrogen and drops into the bath. In neutral or alkaline solutions, much of the scale is reduced to metallic iron, producing a rough, irregular surface.

According to the present invention, the

iron article is made the cathode in an electrolyte containing sulfuric acid, preferably in strong aqueous solution. The scale is thereby reduced to a lower state of oxidation and electrolytically dissolved with the production of ferrous sulfate. An insoluble anode is employed and sulfur or an oxidizable sulfur compound is supplied to the electrolyte, serving by its oxidation to both depolarize the anode and replenish the acid in solution.

In the preferred mode of procedure, the electrolyte consists of an aqueous solution of sulfuric acid having a specific gravity of about 1.20, equivalent to an acid content of 27.1 percent. The anode may be of lead and the current density at the cathode from 40 to 70 ampcres per square foot. The electrolyte is preferably maintained at a temperature of about 60C. Free sulfur or an oxidizahle sulfur-bearing compound, such as supersulfid of a non-alkali metal, specifically pyrite, marcasite or pyrrhotite, is supplied to or maintained at or near the anode and the sulfur is oxidized to trioxidat a rate corresponding to the reduction and solution of the scale on the cathode, thus continuously replenishing the electrolyte. A diaphragm cell may be employed, to retain in proximity to the anode any sulfur dioxid resulting from incomplete oxidation of the sulfur whereby it is finally oxidized to trioxid and prevented from interfering with the cathodic reduction. The production of sulfuric acid corresponds to the rate of its consumption by the formation of ferrous sulfate, the electrolyte thus being maintained at the proper concentration. In the case of a diaphragm cell, the concentration of the acid in the catholyte is maintained by diffusion and cataphoresis from the anolyte.

As the amount of iron sulfate in solution approaches saturation, the electrolyte or catholyte is transferred to a shallow pan and allowed to cool. It is preferable to reduce its temperature to about 0 C. by the use of a suitable refrigerant. The iron sulfate crystallizes out and the residual solution is returned to the electrolytic cell, no evaporation or further treatment being required to fit it for continued use as an electrolyte.

The expression an oxidizable sulfur-bearing material, as used in the claims, is intended to include both free sulfur and sulfur compounds.

I claim:

1. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in passing an electric current to the metal, as cathode, in an electrolyte containing sulfuric acid and a substance capable of yielding sulfuric acid by oxidation, as set forth.

2. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in passing an electric current to the metal, as cathode, in an electrolyte consisting of a strong aqueous solution of sulfuric acid and containing a substance capable of yielding sulfuric acid by oxidation, as set forth.

. 3. The process of electrolytically dissolving iron-oxid scale from the surface of metal,

which consists in passing to the metal as cathode, in an electrolyte consisting of a heat ed,-strong aqueous solution of sulfuric acid,

an electric current of sufficient density to rapidly remove the scale, and maintaining an oxidizable sulfur-bearing material at or in proximity to the anode, as set forth.

4. The process of electrolytically dissolving iron-oxid scale'from the surface ofmetal, which consists in passing to the metal as cathode, in an electrolyte consisting of a heated, strong aqueous solution of sulfuric acid,

anelectric current of sufficient density to rapidly remove the scale, and maintaining a sulfid of anon-alkali metal at or in proximity to the anode, as set forth.

5., The process'of electrolytically dissolving ironoxid scale from the surface of metal which consists in passing to the metal' as cathode, in an electrolyte consisting of a heated, strong aqueous solution of sulfuric acid, an electric current of sufficient density to rapidly remove the scale,.and maintaining T a sulfid of iron at or in proximity to the anode, as set forth,

6. The process of electrolytically dissolving iron-oxid scale from the "surface of metal,

I 7. The process of electrolytically dissolv Zing iron-oxid scale from the surface of metal,

which consists in interposing a diaphragm between a catholyte and anolyte containing dizable sulfur-bearing materlal to the anolyte, as set forth. 8. The process of electrolytically dissolvsulfuric acid, passmg an electric current to the metal, as cathode, and supplying an oxi' ing iron-oxid scale from the surface of metal,

which consists in interposing a diaphragm between acatholyte and anolyte consisting of a heated, strong aqueous solution of sulfuric acid, passing an electric current to the-metal, as cathode, supplying an oxidizable sulfurbearing -mater1al to the anolyte, removing and coolin the catholyte, thereby precipitatingv the ferrous sulfate, and returning the residual solution .to the anode compartment, as set forth.

In testimony whereof, I aflix my signature witnesses. CHARLES J. REED.

Witnesses: t

ROBT. B. FLET HER, a

M; H. QU'INN.

in presence of two 

